/******
* You may use and/or modify this script as long as you:
* 1. Keep my name & webpage mentioned
* 2. Don't use it for commercial purposes
*
* If you want to use this script without complying to the rules above, please contact me first at: marty@excudo.net
*
* Please be aware that this is only the core source-code of a full script and that it may not work (for you) without the rest.
* The full script can be downloaded from my website. A working example is provided there as well.
* 
* Author: Martijn Korse
* Website: http://devshed.excudo.net
*
* Date: 2006-09-07 07:53:21
***/

 // Some global arrays
monthMaxDays	= [31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31];
monthMaxDaysLeap= [31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31];
hideSelectTags = [];

function getRealYear(dateObj)
{
	return (dateObj.getYear() % 100) + (((dateObj.getYear() % 100) < 39) ? 2000 : 1900);
}

function getDaysPerMonth(month, year)
{
	/* 
	Check for leap year ..
	1.Years evenly divisible by four are normally leap years, except for... 
	2.Years also evenly divisible by 100 are not leap years, except for... 
	3.Years also evenly divisible by 400 are leap years. 
	*/
	if ((year % 4) == 0)
	{
		if ((year % 100) == 0 && (year % 400) != 0)
			return monthMaxDays[month];
	
		return monthMaxDaysLeap[month];
	}
	else
		return monthMaxDays[month];
}

function createCalender(year, month, day)
{
	 // current Date
	var curDate = new Date();
	var curDay = curDate.getDate();
	var curMonth = curDate.getMonth();
	var curYear = getRealYear(curDate)

	 // if a date already exists, we calculate some values here
	if (!year)
	{
		var year = curYear;
		var month = curMonth;
	}

	var yearFound = 0;
	for (var i=0; i<document.getElementById('selectYear').options.length; i++)
	{
		if (document.getElementById('selectYear').options[i].value == year)
		{
			document.getElementById('selectYear').selectedIndex = i;
			yearFound = true;
			break;
		}
	}
	if (!yearFound)
	{
		document.getElementById('selectYear').selectedIndex = 0;
		year = document.getElementById('selectYear').options[0].value;		
	}
	document.getElementById('selectMonth').selectedIndex = month;

	 // first day of the month is a ....
	var fristDayOfMonthObj = new Date(year, month, 1);
	var firstDayOfMonth = fristDayOfMonthObj.getDay();

	continu		= true;
	firstRow	= true;
	var x	= 0;
	var d	= 0;
	var trs = []
	var ti = 0;
	while (d <= getDaysPerMonth(month, year))
	{
		if (firstRow)
		{
			trs[ti] = document.createElement("TR");
			if (firstDayOfMonth > 0)
			{
				while (x < firstDayOfMonth)
				{
					trs[ti].appendChild(document.createElement("TD"));
					x++;
				}
			}
			firstRow = false;
			var d = 1;
		}
		if (x % 7 == 0)
		{
			ti++;
			trs[ti] = document.createElement("TR");
		}
		if (day && d == day)
		{
			var setID = 'calenderChoosenDay';
			var styleClass = 'choosenDay';
			var setTitle = 'this day is currently selected';
		}
		else if (d == curDay && month == curMonth && year == curYear)
		{
			var setID = 'calenderToDay';
			var styleClass = 'toDay';
			var setTitle = 'this day today';
		}
		else
		{
			var setID = false;
			var styleClass = 'normalDay';
			var setTitle = false;
		}
		var td = document.createElement("TD");
		td.className = styleClass;
		if (setID)
		{
			td.id = setID;
		}
		if (setTitle)
		{
			td.title = setTitle;
		}
		td.onmouseover = new Function('highLiteDay(this)');
		td.onmouseout = new Function('deHighLiteDay(this)');
		if (targetEl)
			td.onclick = new Function('pickDate('+year+', '+month+', '+d+')');
		else
			td.style.cursor = 'default';
		td.appendChild(document.createTextNode(d));
		trs[ti].appendChild(td);
		x++;
		d++;
	}
	return trs;
}

function showCalender(elPos, tgtEl)
{
	targetEl = false;

	if (document.getElementById(tgtEl))
	{
		targetEl = document.getElementById(tgtEl);
	}
	else
	{
		if (document.forms[0].elements[tgtEl])
		{
			targetEl = document.forms[0].elements[tgtEl];
		}
		else
		{
//			alert('Target field could not be found\nCalender won\'t open therefor');
//			return;
		}
	}
	var calTable = document.getElementById('calenderTable');

	var positions = [0,0];
	var positions = getParentOffset(elPos, positions);	// nieuw
	calTable.style.left = positions[0]+'px';		// nieuw
	calTable.style.top = positions[1]+'px';			// nieuw

	calTable.style.display='block';

	var matchDate = new RegExp('^([0-9]{2})-([0-9]{2})-([0-9]{4})$');
	var m = matchDate.exec(targetEl.value);
	if (m == null)
	{
		trs = createCalender(false, false, false);
		showCalenderBody(trs);
	}
	else
	{
		if (m[1].substr(0, 1) == 0)
			m[1] = m[1].substr(1, 1);
		if (m[2].substr(0, 1) == 0)
			m[2] = m[2].substr(1, 1);
		m[2] = m[2] - 1;
		trs = createCalender(m[3], m[2], m[1]);
		showCalenderBody(trs);
	}

	hideSelect(document.body, 1);
}
function showCalenderBody(trs)
{
	var calTBody = document.getElementById('calender');
	while (calTBody.childNodes[0])
	{
		calTBody.removeChild(calTBody.childNodes[0]);
	}
	for (var i in trs)
	{
		calTBody.appendChild(trs[i]);
	}
}
function setYears(sy, ey)
{
	 // current Date
	var curDate = new Date();
	var curYear = getRealYear(curDate);
	if (sy)
		startYear = curYear;
	if (ey)
		endYear = curYear;
	document.getElementById('selectYear').options.length = 0;
	var j = 0;
	for (y=ey; y>=sy; y--)
	{
		document.getElementById('selectYear')[j++] = new Option(y, y);
	}
}
function hideSelect(el, superTotal)
{
	if (superTotal >= 100)
	{
		return;
	}

	var totalChilds = el.childNodes.length;
	for (var c=0; c<totalChilds; c++)
	{
		var thisTag = el.childNodes[c];
		if (thisTag.tagName == 'SELECT')
		{
			if (thisTag.id != 'selectMonth' && thisTag.id != 'selectYear')
			{
				var calenderEl = document.getElementById('calenderTable');
				var positions = [0,0];
				var positions = getParentOffset(thisTag, positions);	// nieuw
				var thisLeft	= positions[0];
				var thisRight	= positions[0] + thisTag.offsetWidth;
				var thisTop	= positions[1];
				var thisBottom	= positions[1] + thisTag.offsetHeight;
				var calLeft	= calenderEl.offsetLeft;
				var calRight	= calenderEl.offsetLeft + calenderEl.offsetWidth;
				var calTop	= calenderEl.offsetTop;
				var calBottom	= calenderEl.offsetTop + calenderEl.offsetHeight;

				if (
					(
						/* seeing if it overlaps horizontally */
						(thisLeft >= calLeft && thisLeft <= calRight)
							||
						(thisRight <= calRight && thisRight >= calLeft)
							||
						(thisLeft <= calLeft && thisRight >= calRight)
					)
						&&
					(
						/* seeing if it overlaps vertically */
						(thisTop >= calTop && thisTop <= calBottom)
							||
						(thisBottom <= calBottom && thisBottom >= calTop)
							||
						(thisTop <= calTop && thisBottom >= calBottom)
					)
				)
				{
					hideSelectTags[hideSelectTags.length] = thisTag;
					thisTag.style.display = 'none';
				}
			}

		}
		else if(thisTag.childNodes.length > 0)
		{
			hideSelect(thisTag, (superTotal+1));
		}
	}
}
function closeCalender()
{
	for (var i=0; i<hideSelectTags.length; i++)
	{
		hideSelectTags[i].style.display = 'block';
	}
	hideSelectTags.length = 0;
	document.getElementById('calenderTable').style.display='none';
}
function highLiteDay(el)
{
	el.className = 'hlDay';
}
function deHighLiteDay(el)
{
	if (el.id == 'calenderToDay')
		el.className = 'toDay';
	else if (el.id == 'calenderChoosenDay')
		el.className = 'choosenDay';
	else
		el.className = 'normalDay';
}
function pickDate(year, month, day)
{
	month++;
	day	= day < 10 ? '0'+day : day;
	month	= month < 10 ? '0'+month : month;
	if (!targetEl)
	{
		alert('target for date is not set yet');
	}
	else
	{
		//targetEl.value= day+'-'+month+'-'+year;                      //********* edit here if you want to change the fomrula of the date ;)
		targetEl.value= year+'-'+month+'-'+day;
		closeCalender();
	}
}
function getParentOffset(el, positions)
{
	positions[0] += el.offsetLeft;
	positions[1] += el.offsetTop;
	if (el.offsetParent)
		positions = getParentOffset(el.offsetParent, positions);
	return positions;
}